1. Field of the Invention
The present invention relates to a resin component for encapsulating a semiconductor and more particularly to a resin component for encapsulating a semiconductor in which a curing body has an electromagnetic wave shielding function and insulating characteristics.
2. Description of Related Art
In a manufacturing process of a semiconductor device, a semiconductor element whose bonding to a substrate is completed is encapsulated by employing a molded resin such as a thermosetting resin in order to avoid a contact with an external part. As the molded resin, for instance, there is employed a material obtained by mixing and dispersing an inorganic filler including silica powder as a main component in an epoxy resin. As the encapsulating method, for instance, has been put to practical use a transfer molding method in which the semiconductor element bonded to the substrate is inserted into a die, and the molded resin is supplied under pressure thereto and is cured to be molded.
A resin encapsulated type semiconductor device in which a semiconductor element is encapsulated by a molded resin has been hitherto excellent in view of reliability, mass-productivity and low cost, so that this semiconductor device has been popularized as well as a ceramic encapsulated type semiconductor device which is encapsulated by using a ceramic case having a ceramic material as a component material.
In an electronic device, an EMC (Electro-Magnetic Compatibility) has been paid attention to. For instance, in recent years, the development of compact and highly functional information communication devices has been advanced. For obtaining the higher functions of semiconductor elements used in such devices, the operating frequencies of them have been more raised. Especially, in increasing the speed of a digital signal, the amplitude of the signal has been decreased in order to reduce consumed power. As a result, there has been increased a possibility that the semiconductor elements may cause malfunctions even under small and weak high frequency noise. Therefore, the development of the electronic devices which do not emit unnecessary electromagnetic waves or have durability relative to the electromagnetic waves generated in the circumference has progressed.
As one of the countermeasures of such a problem, there has been proposed a method that the semiconductor element is covered with a metallic cap so that electromagnetic waves generated by the semiconductor element or electromagnetic waves generated by the circumference are discharged outside the semiconductor element. However, in this method, since a mounting space in which the metallic cap is disposed is required, the packaging density of the electronic device cannot be raised, and accordingly, it is difficult to meet a compact device.
Thus, an electromagnetic wave shielding technique suitable for a high density mounting has been necessary and a method for providing an electromagnetic wave shielding function in a molded resin has been proposed.
However, when the conventional resin component obtained by mixing and dispersing only the filler including the silica powder as the main component in the epoxy resin is employed as the molded resin, the curing body for encapsulating a semiconductor element does not exhibit the electromagnetic wave shielding function.
In Japanese Patent Application Laid-Open No. hei 3-23654, a method for using a molded resin in which ferrite powder is mixed is proposed in order to prevent the entry of electromagnetic waves. When only the ferrite powder is independently employed for a filler of epoxy resin, a curing body for encapsulating a semiconductor element has the electromagnetic wave shielding function, however, the resin flashes may be formed inside a die upon molding, so that, sometimes, an excellent curing body cannot be obtained.
In Japanese Patent Application Laid-Open No. hei 6-151626 and Japanese Patent Application Laid-Open No. hei 11-40708 or the like, a molded resin in which ferrite powder is mixed is likewise proposed, however, its moldability is not described.
Further, since the curing body for encapsulating the semiconductor element includes ferrite, there exist a risk that electric current may leak to cause the malfunction of the semiconductor element due to the contact of the semiconductor element with the curing body depending on the kinds or content thereof.